Liquid transfer system



Sept. 3, 1968 K. F. scnocm ET AL 3,399,691

LIQUID TRANSFER SYSTEM 2 Sheets-Sheet 1 Filed Aug. 15, 19661771/6272202: Kar/ F S'cboc/7. Andrem/ Sept. 3, 1968 K. F. scuocu ET AL3,399,691

LIQUID TRANSFER SYSTEM 2 Sheets-Sheet 2 F'iled Aug. 15, 1966 UnitedStates Patent O 3,399,691 LIQUID TRANSFER SYSTEM Karl F. Schach, Scotia,and Andrew I. Dahl, Schenectady N.Y. assignors t General ElectricCompany, a cor poration of New York Filed Aug. 15, 1966, Set. N0.572,526 14 Claims. (Cl. 137-375) ABSTRACT OF THE DISCLOSURE A liquidhelium transfer system includes a liquid helium pump for transferringhelium through a cooled flexible transfer line into a receiving vessel.A sensor in the vessel controls operation of the umps so that a constantlevel of helium is maintained in the receiving vessel even though thehelium is pumped at variable flow rates.

Our invention relates to a liquid transfer system and in particular to asystem for transferring low temperature liquids to operating apparatus.

The invention described herein was made in the performance of work undera NASA contract and is subjeet to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 U.S.C. 2457).

In former practice, liquid helium has been transferred from liquefiersto storage Dewars and from storage Dewars to cryostats by batchtransfer. In some applications such as in a superconducting gyro, batchtransfer is not the most desirable system since the use of batchtransfer t0 a cryostat results in large thermal gradients and this maycause difliculties with instrumentation and precise angular alignmentsof the mechanical structure on which the gyro is mounted. One way ofremedying these difliculties is to have a continuous flow at a ratesuitable to keep the cryogenic liquid in the cryostat at a substantiallyconstant level. In order to maintain liquid in a cryostat at asubstantially constant level, the system must continuously pumpcryogenic liquid at a regulated rate into the cryostat.

An object of our invention is to provide a system capable of supplying acryogenic liquid to a container.

Another object of this invention is a system capable of automatic flowcontrol to maintain constant liquid helium level in a cryostat.

Another object of this invention is to provide a transfer system whereinheat transfer into or out of the system is at a minimum.

Another object of this invention is to provide a cryogenie transfersystem wherein part of the transfer line is flexible and a rotary jointis also provided.

In brief, our liquid transfer system transfers small increments ofliquid from a first container to another with a minimum loss 0r gain ofheat to the liquid being transferred. A tube with a pump on its end isinserted into the liquid and the other end of the tube extends out ofthe first container and into a flexible section. The flexible sectionhas several layers of nonheat conducting material and a transfer lineconnected to one of its ends. The transfer line has an inner pipe forcarrying the liquid and several thicknesses of cooling and nonheatconducting material. At the other end of the insulating line a rotarycoupling is attached to the line. The coupling is fashioned ofconcentrie pipes for insulation and provides a conduit for the liquid t0pass into a second container. The second container has sensors to eausethe pump in the first container to pump more liquid When the level inthe second container decreases below a given level and to slow pumpingWhen the level rises above a predetermined point.

Patented Sept. 3, 1968 Although the embodiment described herein showsour invention as applied t0 a cryogenie liquid being transferred to acryostat, it is understood that our invention will apply to the transferof any liquid. For example, our invention may be used t0 maintain thelevel of hydrogen 01' the like in a liquid propellant missile which isin a state of readiness but for some reason one wishes to hold it onstandby for a time.

The novel features which are believed to be characteristic of theinvention are set forth in the appended claims. The invention itself,however, together with further objects and advantages thereof may bestbe understood by 'reference to the following description taken inconjunction with the accompanying drawings in which:

FIGURE 1 shows a schematic arrangement of our liquid transfer apparatus.

FIGURE 2 shows the construction details of a flexible section in thetransfer line.

FIGURE 3 shows the construction -details of the rotary joint at thepoint of attachment to the cryostat.

FIGURE 4 shows the structure of a supercond-ucting pump.

The general arrangement of the elements of the liquid helium transfersystem in FIGURE 1 shows liquid helium being transferred from aconventional 50 to liter Dewar container to a cryostat. In thisembodiment, a cryostat 1 is mounted on a sidereal test table 0f the typeactuated by clock work and designed to turn the table top so that it isoriented in space in a constant position, i.e., as the earth moves thetable top turns to compensate for the earths motion and to preserve theosition of the table top in relation to the stars.

Test table 2 is rotated at the earths rotational rate about an axisparallel to the axis of a rotary coupling 3 and a transfer line 4.Rotary coupling 3 of this line permits the cryostat to be turned With0utinterruption to the flow of liquid helium through the transfer line. Itis contemplated that the rate of flow of liquid helium from the Dewarsupply tank to the cryostat Will be on the order of 1 liter per hour.The line is cooled and shielded with liquid nitrogen to preventexcessive evaporation of liquid helium. When the system operates, liquidhelium is in the line at all times. A short section of flexible line 6is provided to isolate the cryostat from mechanical disturbances whichmight arise. A superconducting pump 7 located at a low level inside theDewar flask 5 is electrically operated by 60-cycle current andcontrolled by two thermistors located in cryostat 1 and responsive t0the liquid level in the cryostat. One thermistor is located above thedesired liquid level and one is immersed in the liquid at the desiredliquid level. When the lower thermistor is out of the liquid, a controlcircuit (not shown) actuates a relay valve so that liquid transferbegins, the rate of transfer decreasing When the high level sensor iscovered by the liquid. Thermistors are employed because of theircharacteristics of high temperature coefiicient, small size and lowpower dissipation. Valves, inlets and outlets are provided at intervalsalong the cond-uit to allow passage of liquid nitrogen and evacuation ofair. A nitrogen fill tube may be used to introduce liquid nitrogen.

In operation of the pump 7 (FIGURE 4), if the liquid level in thecryostat drops somewhat, the amplitude of 60 cycle current supplied to asuperconductive coil 40 is increased. When current asses through thecoil, pressure is exerted 0n the superconducting piston 41 and bellows42 of pump 7 to move it upwardly a few thousandths of an inch at eachstroke. The upward motion forces liquid through a pump valve 43 intosmall tube 8 and out into transfer line 4. When current decreases in thecoil, the bellows pushes the piston back toward the coil and the bellowsrefills through inlet port 44 and valve 45 for an other pump stroke.

The pump pistons motion is of small amplitude and the amount of heliummoved per stroke is relatively small. The electrically operated heliumpump is of small capacity and pumps by small increments per stroke thusassuring continuous flow. While details of the pump illustrated aredescribed in an article by T. A. Buchhold and B Barrel in Cryogenics,April 1965, page 109, any suitable pump may be used and forms no part ofthis invention.

The transfer line comprises four concentric tubes (FIGURE 2). Theinnermost tube 9 is made of a material having a low tliermal coefiicient013 expansion such as, for example, Invar nickel alloy. A second tube 10made cf similar material to tube 9 surrounds tube 9 and is spacedtherefrom by a spacer made 01 a substance, for example, nylon, having arelatively low heat conductance. A third tube 12 surrounds tube 10 andis spaced therefromby similar low heat conducting elements. Surroundingtube 12 and spaced from it is a fourth tube 13 which forms the outercovering for the transfer line. The outer tube 13 is made of a materialhaving the qualities of low heat conductivity and duxability, such asstainless steel nurnber 347. Tube 13 functions to protect the innerparts of the line and to avoid heat transfer through it. Tubes 9, 10 and12 preferably are made of a material having a low therrnal coefficientof expansion. These tubes fluctuate in temperature from ambienttemperature when empty to a very low temperature when a liquid likehelium is passed through the transfer line.

The spaces beween the first and second tubes 9, 10 and the third andfourth tubes 12, 13 are evacuated to prevent heat loss by convection ofair in the spaces. The space between the second and third tubes isfilled with a ther-mal radiation shielding material, such as, forexample, liquid nitrogen.

FIGURE 2 shows the construction details of the flexible section 6, theinnermost element of which is an elongated bellows 14 made of aresilient material such as bronze which does not become brittle at lowtemperatures. Bellows 14 acts as a conduit for the liquid helium and isin function an extension of the innermost tube 9 of the transfer linewhich in turn is an extension of tube 8. Several layers of a reflectivesheet material 15 such as aluminized Mylar are wrapped about the bellowsWith the reflective surfaces outward. A cord 16 made of a nonconductingflexible material, for example, nylon, is loosely spiraled about thereflective sheet material and serves as spacing for a flexible radiationshield 17, 18

made of flexible, reflective and conductive ribbon material such ascopper foil. The shield is made of two er more layers of ribbon 17, 18,spiraled one over the other in opposing directions to give flexibilityand maximum radiation protection. The ends 19 of the ribbon axe wrappedonto one end 01 tube 12 Which contains liquid nitrogen supplied throughliquid nitrogen input tube 4' (FIG 1). This connection allows conductioncooling of the sh-ield 17, 18 along its extent. Outside the shield arelayers of a thin sheet nonconductive material having a reflectivecoating such as aluminized Mylar 15'. Surrounding this is an elongatedunter bellows element 20 which extends the entire length of the flexiblesection.

The liquid nitrogen filled annulus tubes 10 and 12 and the helium tube 9are made of Invar tubing to minimize contraction due to temperaturechange. The outer bellows 20 is made of a resilient, durable,nonconductive material like type 321 stainless steel.

The rotary coupling 3 shown in FIGURE 3 provides the attachment betweenhelium transfer line 4 and cryostat 1 (FIGURE l). This coupling allowsrotation of the cryostat relative to the helium transfer line 4. Of thesix concentric tubes in this coupling, the outer three 21, 22, and 23,form an integral element sealed to the cryostat and the inner three 24,25, and 26, form a male element 27 which is attached to the transferline and is insertable into the female element 28 and can be fastenedto-it.The

male assembly has a gland nut 33 attached to it for forming a leakproofrotatable connection between the male and female assemblies. Liquidhelium asses through the center tube 24 of the male assembly and througha bellows 29 and then into the inner tube 30 attached directly to thecryost'at assembly. Tube 21 is made of a durable, nonheat-conductingmaterial like stainless steel number 347 while the other tubes of themale and female fittings can be made of a material having low thermalcoeflficient of expansion such as Invar. Preferably tubes 22 and 25 aremade of a heat conducting material such as copper. In order to keep tube22 cool, a braided heat conductive element 34 conducts heat from tube 22to the inner wall 0f cryostat 1. The bellows 29 is attached at one endto the inner of the three inner tubes and has upon its other end aslidable coupling 31 which slides on Coupling element 32 attached to thetube 30 leading into the cryostat. Bellows 29 exerts some pressure uponwaferlike member 31 and this member rests on element 32. This connectionpoint is substantially closely sealed. Since the bellows keeps a slightpressure upon the connection point, little or no helium is lost betweencoupling 31 and element 32. The bellows allows for pressure variationsand mobility depending upon conditions 0f transfer. If helium leaks bythe sliding surface at 31, 32 it will vaporize and build up pressuretendingto equalize the pressure across the joint.

An advantage of this apparatus is that it provides for the virtuallycontinuous but slow filling of a container to a predetermined level.Rather than batch transfer, euch pumping increment is of smalldisplacement and avoids the temperature pumping gradients anddiscontinuity inherent in batch transfer of liquid helium.

Another advantage is that it provides for transfer 0f low temperatureliquid from one container to another With a minimal of heat gain andminimal loss 0f low temperature liquid.

The foregoing is a description of an illustrative embodiment of theinvention, and it is applicants intention in the appended claims tocover all forms which fall within the scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. In a liquid supply system for conducting a liquid from a storagepoint to a container the combination of:

a liqlid conducting tube having a pump attached to one a flexibleinsulated section for connecting said tube to an insulated transferline,

an insulated transfer line connected to said flexible insulated section,

an insulated rotary coupling tubular section connected between saidinsulated line and a container so as to pass liquid from said line tosaid container.

2. The liquid supply system of claim 1 in which the conducting tube ismade of a material having a low thermal coefficient of expansion.

3. The liquid supply system of claim 1 in which the transfer linecomprises a plurality of diflerent sized tubes mounted concentrically.

4. The liquid supply system of claim 1 in which the transfer linecomprises:

a first inner tube made of a material having very low thermal expansionproperties,

a second larger tube coaxial With said first tube and spaced from saidfirst tube,

a third tube coaxial with said second tube and spaced therefrom, and

a fourth outer tube coaxial with said other tubes,

spaced from said third tube and made 01 a durable material.

5. The liquid supply system of claim 4 with the addition oft means forevacuating the spaces between said first und second tubes and said thirdand fourth tubes.

6. The liquid supply system of claim 4 with the additiom of:

meams for imtroducimg a shieldimg liquid imto the space betweem thesecomd and third tubes.

7. A rotary fittimg for a liquid tramsfer system for transferrimg liquidfrom storage imto a comtaimer comprisimg:

a male assembly adapted to fit snugly imside a female assembly, saidmale assembly havimg:

an immer tube,

an imtermediate tube spaced from said immer tube and extemding aroundsaid immer tube for about half the lemgth of said male assembly,

an exterior tube spaced from said imtermediate tube and extemdimg thelemgth of said immer tube,

an ammular spacer commectimg the emds of said immer tube and saidexterior tube,

a glamd mut slidable 0m said male assembly,

a flexible fittimg adapted to form am extemsiom of said immer tube andfastened to said immer tube at said ammular spacer, said female assemblyhavimg:

am immer tube 0f a size larger tham the exterior tube of said maleassembly and havimg at one emd am ammular elememt (32) which slidablyemgages said flexible fittimg of said male assembly and havimg a tubeattached to the immer edge of said ammular elememt so that liquid may bepassed therethrough,

am imtermediate tube larger tham said immer tube and spaced therefromwith one emd mear the middle of said immer tube, the other emd of saidimtermediate tube extemdimg imto said comtaimer,

am exterior tube havimg momheat comductimg spacers betweem it and saidimtermediate tube mear said other emd of said imtermediate tube,

a cylimdrical fittimg havimg at one emd a partially threaded outersurface and its other emd fastemed betweem said exterior tube and saidimmer tube, the threads of said cylimdrical fittimg cooperatimg withsaid glamd mut to allow a rotatable commectiom betweem said maleassembly and said female assembly.

a flexible cord of insulatimg material woumd about said reflectiveimsulatiom,

a shield made of ribbom and reflective imsulatiom and wrapped about saidflexible cord,

am outer bellows surroumding said shield and extendimg the lemgth ofsaid flexible sectiom,

fittimgs to commect said bellows to the rest of a liquid tramsfersection.

10. A flexible seetiom for a liquid tramsfer system as set forth imclaim 9 whereim said shield is:

a heat comductive ribbom woumd about said flexible cord im a spiral, and

a secomd heat comductive ribbon woumd im a reverse direetiom about saidfirst ribbom whereby the two ribboms form a flexible shield.

11. Am imsulated transfer lime for tramsfer of liquid comprising:

am immer tube extemdimg the lemgth of said lime and made 0f materialhavimg a low thermal coefliciemt of expamsion,

a secomd tube surroundimg said immer tube, spaced from said immer tubeand made of similar material as said immer tube,

a third tube surroundimg said secomd tube, spaced from said secomd tubeand made of a similar material as said other tubes,

a fourth tube surroumdimg said other tubes, spaced from said other tubesand made of a durable material havimg low heat comductivity.

12. Am imsulated tramsfer lime as set forth im claim 11 whereim:

spacers made of nomheat comductimg material are used betweem said tubesto maimtaim said tubes apart. 13. Am imsulated transfer lime as setforth im claim 11 im which:

am evacuation tube is conmected to the spaces betweem the first andsecomd tubes and the third and fourth tubes to evacuate said spaces. 14.Am imsulated tramsfer lime as set forth in claim 11 in which:

a filler tube is commected to the spaee betweem the secomd and thirdtubes to allow the imtroductiom of a shield- HENRY T. KLINKSIEK, PrimaryExaminer.

